Rust-inhibiting compositions



Patented Nov. 13, 1951 RUST-INHIBITING COMPOSITIONS John W. Bishop, Roselle, N. J., assignor to Tide Water Associated Oil Company, Bayonne, N. J., a corporation of Delaware No Drawing. Application September 23, 1947, Serial No. 775,755

4 Claims.

The present invention relates to rust-inhibiting compositions and to the use thereof for inhibiting rusting of metal surfaces. More particularly, the invention relates to compositions,

of highly effective rust-inhibiting characteristics and particularly adaptable for prevention of rusting of ferrous metals upon exposure to humid atmospheres or other atmospheres inducing metal corrosion. Hence, in practical aspect, the rust-inhibiting compositions, as embodied herein, are adaptable for protection of metal surfaces of machine parts, engines, drums, and the like, against rusting during transportation or storage or when subjected to other conditions inducing rusting thereof. Furthermore, the rustinhibiting compositions, as embodied herein, are adaptable for use in lubricating oils, as for example, turbine lubricating oils, motor lubricating oils, and the like; with resulting protection of metal parts thereof with which the oil composition is brought into contact.

Generally speaking, the rust-inhibiting compositions, as embodied herein, comprise in essential combination an acid ester of a phosphorus acid and an esterified alkylolamine, i. e., an amine such as may be obtained by esterification of an alkylol group of an alkylolamine with an organic acid. Although the two-component composition may, for certain purposes, be suitable per se as a rust-inhibiting composition for protection of metal surfaces by coating the metal surfaces therewith, in a more practical embodiment, the compositions, as embodied herein are used as solutions comprising i a major proportional amount by weight of a solvent vehicle blended with the aforedescribed two component additive. The solvent vehicle may comprise any of various types of suitable liquid mediums in which the two component additive is soluble. Preferably, the solvent vehicles employed are of the volatile and/or non-volatile type hydrocarbons such as i the non-drying substantially non-volatile type of oils derived from mineral oils and fractions thereof, as for example hydrocarbon lubricating oils, greases, petrolatum, and the like, and volatile substances of the aliphatic and aromatic types such, for example, as naphtha, benzene, and similar substances. When used in this manner the rust-inhibiting agent-containing solutions provide economical and easily applied compositions for use as coatings for metal surfaces to be protected against rusting. Moreover, when the rust-inhibiting agent of the present invention is incorporated into oils used for lubrication purposes, the resultant oil composition serves a dual function in preventing formation of rust on the interior parts of internal combustion engines, turbines, or other mechanisms with which the composition is in contact while at the same time providing satisfactory lubricating properties.

With reference to the acid esters of a phosphorus acid which comprise one of the two essential components of the rust-inhibiting agent embodied herein, it is preferred to employ acid esters of orthophosphoric acid and, more particularly, acid esters thereof containing at least one relatively long alkyl group, as for example, on the order of at least eight, and more preferably eight to twenty carbon atoms. Particularly suitable esters falling within the foregoing preferred classification may be illustrated by acid esters such as mono lauryl acid phosphate and dilauryl acid phosphate. Hence, in my description of the invention, as set forth hereinafter, the invention is described, for purposes of illustration, with reference to use of lauryl and phosphate esters.

The other essential component of my rust-inhibiting agent may be broadly described as an esterified alkylolamine, such as may be obtained by esterifying an alkylol group of an alkylolamine with an organic acid. Suitable examples, of amines that may be employed for preparing the esterified alkylolamines may be illustrated by the ethanol amines, e. g., mono-, di-, and triethanol amines. In a preferred embodiment, the esterified alkylolamines employed herein are those obtained by esterification of alkylolamines, e. g., such as an ethanol amine, with a long chain organic acid, as for example, an aliphatic acid having about 4 to 30 carbon atoms and more preferably about 8 to 20 carbon atoms; particularly preferred acids that may be used for the esterification may be illustrated by aliphatic acids having a long carbon chain, such as in stearic acid, oleic acid, lauric and the like. Still further, particularly suitable esterified alkylolamines, such as may be employed with highly satisfactory results in practicing this invention, may be illustrated by B (N-diethyl) aminoethylstearate, such as may be prepared by esterifying the ethanol group of diethyl ethanolamine with stearic acid, B (N-ethanol) aminodi (ethyloleate) such as may be obtained by esterifying two ethanol groups of tri-ethanolamine with oleic acid, and B (N-diethyl) aminoethyloleate, such as may be obtained by esterifying the ethanol group of diethyl ethanolamine with oleic acid, and the like.

The aforedescribed acid phosphate esters and esterified alkylolamines, when used individually in mineral oil compositions, usually impart thereto a certain degree of rust-inhibiting characteristics, and forsome purposes, individual use of either of such compounds may provide a satisfactory degree of rust preventive properties to the oil. However, for many usages, such as when metal surfaces are exposed to very severe corrosion-inducing conditions, it is highly desirable to employ compositions that are more highly effective in rust-inhibiting properties than is obtainable by individual use of either the acid phosphate ester or the esterifled alkylolamine. In accordance with the present invention, I have found that by using in combination the aforedescribed acid phosphate esters and 'esterifled alkylolamines and in certain molecular proportions, very marked improvements in rust-inhibiting characteristics are obtained. In fact, the use in combination of the foregoing described compounds has been found to provide rust inhibiting characteristics that are unexpectedly and materially higher than are obtainable by individual use of either component in substantially equivalent concentrations to the two component rustinhibiting agents.

In order to further describe my invention, several examples are set forth hereinafter illustrating the markedly improved rust-inhibiting characteristics imparted toan oil by incorporating therein the two component additive of the present invention. Furthermore. and in order to show the marked improvement resulting from use of the two-component agent as compared to individual use of either component, several examples are included which relate to the individual use of an acid phosphate ester or an esterifled alkylolamine. Each of the examples set forth hereinafter was subjected, for determination of rustinhibiting characteristics, to the conditions of the humidity corrosion test described in Army-Navy Aeronautical Specification Compound: Corrosion Preventive, Aircraft Engine, AN-VV-C-576B, April 28, 1945." Briefly, the test comprises coating two freshly sandblasted steel panels with the test composition, draining for four hours in an atmosphere maintained at a relative humidity not exceeding 50% and a temperature of C. (plus or minus 3' C.) and then subjecting the panels to a circulating atmosphere of 95 to 100% relative humidity at a temperature of 120 F. for 150 hours, or for a longer period to determine rust-inhibiting characteristics of test compositions under more severe conditions. At the end of the test period, the panels are removed from the humidity cabinet, cleaned with naphtha, and examined. The presence of any corrosion on the panel, except within from any edge thereof evidences failure of the composition.

Ezample I In order to determine the rust-inhibiting characteristics obtained by use of an esterifled alkylol-" amine, compositions were prepared by blending a Mid-Continent 1120 grade aviation oil with amounts of B (N-diethyD' aminoethylstearate varying from 2 to 4% based on the weight of oil. When subjected to the conditions of the aforedescribed humidity test, these compositions had a humidity test life of about 150 hours.

Example II Example 11! A composition was prepared by blending an aviation grade oil (as used in Examples I and II) with 2% by weight of B (N-diethyl) aminoethylstearate and 3% of the acid lauryl phosphate mixture described in Example II. In this composition, the mole ratio of the esterified alkylolamine to the phosphate acid esters was about 1:1.5. When subjected to the aforedescribed humidity cabinet test, this composition had a test life of more than 1680 hours.

Referring to Example I, wherein 2 to 4% of the esterifled alkylolamine was used and provided a test life of hours, and to Example II wherein 3 to 5% of acid lauryl phosphates was used and provided a humidity test life of not more than 150 hours, the additive humidity life of a composition containing 2% of the esterified alkylolamine and 3% of the acid phosphate esters would normally be expected to be not more than 250 to 300 hours. However, as is clearly illustrated by this example (the composition of Example III), use of a combination of 2% of the esterified alkylolamine and 3% of the acid phosphate esters gave an unexpected high increase in rust preventive characteristics in that the humidity life exceeded 1680 hours which is more than 5 times greater than the additive life obtained by individual use of the esterified alkylolamine and the acid phosphate in the aforestated concentrations.

Example IV The following are additional illustrations of compositions, using in combination the same Composition No. l 2 3 Percentage by Weight Mid-Continent, 1120 Grade $113106. (ailqflgughnisugtfl 97.5 95.5 99.17

0e feufhfl? .Z 1.0 2.0 0.33 Lauryl acid phos hates 1.6 2.5 0.5

Mole ratio of (N-diethyi) aminoethylstearate to Lauryl acid hosphate 1:1.5 121.25 1:1.5 Humidity Test Life in Hours... over 1, over i, 680 500 Example V The following compositions are set forth to further illustrate that highly effective rust inhibiting characteristics are obtained by use of compositions, similar to those in the foregoing examples except that esterified alkylolamines other than B (N-diethyl) aminoethylstearate were employed.

containing the two-components additive, gave a humidity life of about 1,000 hours, use of either B (N-ethanol) amino-di(ethyloleate) or B(N- diethyl) aminoethyloleate in concentrations of 4% based on the weight of oil gave humidity values not exceeding about 150 hours, again illustrating the considerably higher than additive results obtained by use of the two-component additive.

In all of the foregoing illustrative examples,

I wherein the combination additive was employed,

the acid phosphate ester was used in an amount in excess of a mole to mole ratio with the esterified alkylolamine. Moreover, in each case, it has been clearly shown that the combination additive provides unexpectedly high rust-inhibiting characteristics. It is an important aspect of the present invention that the acid phosphate ester be employed in a ratio of not less than one mole to one mole of the esterified alkylolamine. More preferably, and in order to obtain very marked improvements in rust-inhibiting characteristics, the phosphate acid ester should be employed in an amount in excess of a mole to mole ratio with the esterified alkylolamine. Referring to the compositions set forth in Examples III to V, the ratio of esterified alkylolamine to the acid phosphate ester as used therein varies from one mole of the amine to about 1.1 to 1.5 moles of the acid phosphate ester. With such a ratio of components. exceptionally high humidity test life was obtained as evidenced by the values set forth in the foregoing examples. Although use of the two-components in substantially mole to mole ratio may provide some improvement in rustinhibiting characteristics as compared to individual use of either of the two-components, the improvement is considerably less than is obtained by use of an excess of the acid phosphate ester as discussed hereinbefore. For example, a composition was prepared comprising 2 parts by weight of B (N-diethyl) aminoethylstearate and 2 p rts by weight of the aforesaid described lauryl acid phosphates wherein the two components were in substantially mole to mole ratio. When subjected to the aforedescribed humidity cabinet test, the composition gave a humidity test life of 200 hours. Comparing these results with those obtained in Example III, employing a composition containing the same esterifled alkylolamine and acid phosphate esters and in which the same concentration of amine was used but in which an excess of phosphate ester was used, use of an excess of the acid phosphate ester increased the humidity life from about 200 hours to 1600 hours. Accordingly, in a preferred embodiment of the present invention, the rust-inhibiting agent not only contains in essential combination of the aforedescribed esterifled alkylolamines and acid phosphate esters, but contains the acid phosphate ester in an amount in excess of a mole to mole ratio with the amine. Although, as hereinbefore set forth, a highly effective ratio of components is one mole of the amine to 1.1 to 1.5 moles of the phosphate ester, a greater excess of phosphate esters may be suitably employed, as for example. about 2 to 3 moles of the phosphate ester; to 1 mole of the amine, although for most purposes. the aforesaid proportions provide a degree of rust-inhibiting characteristics sumcient to afford protection even under very severe rustenhancing conditions.

As is apparent to those skilled in the art, the desired total concentration of the two-component additiveincorporated into a solvent vehicle, as for example a mineral oil, will depend to a considerable degree on factors such as the degree of rust-inhibiting characteristics desired, solubility characteristics of the rust-inhibiting agent in the solvent vehicle employed, and the like.

Thus for example, in preparing mineral oil com-' positions containing the two-component additive, the total concentration of additive. employed may vary over rather wide limits depending on the severity of the rust-inducing conditions against which metal protection is desired. For most purposes, however, a total concentration of the additive varying from about 0.01 to 20% by weight based on the oil is satisfactory, the lower concentrations being employed for conditions that are not too severe toward enhancing metal rusting, and the higher concentrations for use to protect metals against extremely severe rust-inducing conditions. For use in lubricating oils, such as of the turbine grade, and in rust-preventive oil compositions, wherein the rust-inducing conditions may not be very severe, a total concentration of as low as about 0.01% of the two component-additive may be used, in which case the amine should be used in at least about 0.005% by weight. However, when excessively high degree of protection is desired, a higher concentration is employed, as for example, up to about 20% by weight and on the order of the additive concentration and ratio of components thereof as set forth in the foregoing examples.

In preparing mineral oil compositions containing an esterified alkylolamine and an acid phosphate ester as aforedescribed, the two components may be added to the mineral oil either individually or in combination. Still further, the two-component additive may be prepared as a concentrate in desired proportions as a dispersion or solution in a suitable solvent. For example, the two component additives may be prepared as a concentrate in a mineral oil, or fraction thereof, and added as such to oil compositions that are to be imparted with rustinhibiting'characteristics in accordance with the present invention.

Although the exact nature of the reasons underlying the high degree of rust prevention resulting from practice of the present invention is not fully known, such phenomena obviously occurs as is apparent from the data set forth hereinbefore Showing the markedly improved results obtained by using in the stated concentrations and ratios the two-component additive as embodied herein, especially when the results obtained therefrom are compared with individual use of either component thereof. By practicing the present invention, not only are highly effective rust-inhibiting characteristics obtained, but the oil compositions obtained are also highly satisfactory in having strong wetting action upon and adherence to metal surfaces while at the same time provide substantially unbroken films under quite adverse conditions which is a highly desirable characteristic of rust preventive compositions.

Although it is not intended that the present invention be limited by any theory underlying possible reaction of the two components of the rust-inhibiting agent, it is believed that the esterified alkylolamines and acid phosphate esters form a loosely bound addition product, the

addition taking place at the nitrogen atom of the esterlfied alkylolamine with a hydroxyl group of the acidic phosphoric acid ester. Hence, on such a basis, and following the highly preferred practice of the invention in using an aforedescribed excess of acid phosphate ester, suflicient phosphate ester is employed to form addition products with the amine and to provide an excess of the acid phosphate ester.

Although the present invention has been described in conjunction with certain preferred embodiments thereof, those skilled in the art will readily recognize that variations and modifications can be made. Such variations and modifications are to be considered to be within the purview of the specification and the scope of the appended claims. Moreover, although the invention has been described with particular reference to oil compositions containing the two component agent, it is within the scope of the invention to increase the rust-inhibiting characteristics of an oil containing an esterlfied alkylolamine by incorporating an acid phosphate ester therein, and similarly, by incorporating an esterlfied alkylolamine in an oil containing an acid phosphate ester, the addition of either the amine or phosphate ester being in accordance with the mole ratios as hereinbefore set forth.

I claim: Y

1. A composition, adapted for inhibiting rusting of metal surfaces, comprising a hydrocarbon vehicle in major amount based upon the weight of said composition having dissolved therein as a rust-inhibiting component from about 0.01 to about 20% by weight of a loosely bound addition product of acid lauryl phosphate and a tertiary ethanol amine esterlfied with a fatty acid from the group consisting of stearic acid and oleic acid, said esterlfied amine being present in a ratio of one mole of amine to about one to one and a half moles of the acid phosphate.

2. A composition, as defined in claim 1, wherein the amine is a member from the group con- 8 sisting of. tertiaryalkyl ethanol amines and triethanolamine.

3. A composition, adapted for inhibiting rusting of metal surfaces, comprising a hydrocarbon vehicle in major amount based upon the weight of said composition having dissolved therein as a rust-inhibiting component from about 0.01 to about 20% of a loosely bound addition product of an alkyl acid phosphate containing an alkyl group of about eight to about twenty carbon atoms and a tertiary alkylolamine containing an alkylol group esterlfied with a fatty acid of about eight to twenty carbon atoms, said esterified amine being present in a ratio of one mole of amine to about one to about one and a half moles of the acid phosphate.

4. A composition, as defined in claim 3, wherein the alkyiolamine is a member from the group consisting of tertiary alkyl alkylolamines and trialkylolamines.

JOHN W. BISHOP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,080,299 Benning May 11, 1937 2,162,454 Guthman June 13, 1939 2,238,478 Ott Apr. 15, 1941 2,261,888 Rocchini Nov. 4, 1941 2,291,066 Waugh -2... July 28, 1942 2,382,699 Duncan Aug. 14, 1945 2,413,852 Lurner Jan. 7, 1947 2,430,846 Morgan Nov. 11, 1947 2,442,581 Bishop June 1, 1948 2,450,807 McCarthy Oct. 7, 1948 FOREIGN PATENTS Number Country Date 814,698 France Mar. 22, 1937 

1. A COMPOSITION, ADAPTED FOR INHIBITING RUSTING OF METAL SURFACES, COMPRISING A HYDROCARBON VEHICLE IN MAJOR AMOUNT BASED UPON THE WEIGHT OF SAID COMPOSITION HAVING DISSOLVED THEREIN AS A RUST-INHIBITING COMPONENT FROM ABOUT 0.01 TO ABOUT 20% BY WEIGHT OF A LOOSELY BOUND ADDITION PRODUCT OF ACID LAURYL PHOSPHATE AND A TERTIARY ETHANOL AMINE ESTERIFIED WITH A FATTY ACID FROM THE GROUP CONSISTING OF STEARIC ACID AND OLEIC ACID, SAID ESTERIFIED AMINE BEING PRESENT IN A RATIO OF ONE MOLE OF AMINE TO ABOUT ONE TO ONE AND A HALF MOLES OF THE ACID PHOSPHATE. 